From df3eb0a366c7846910907d6640225a2e3316b7ba Mon Sep 17 00:00:00 2001
From: Aleksandr Emelenko <emelenko.aleksandr@huawei.com>
Date: Fri, 12 Aug 2022 15:20:44 +0300
Subject: [PATCH] [Runtime] Optimize usage of the internal allocator inside
 class linker

Change-Id: I149f6a6cc0c09c499fdfa50dbbe9a3e461ca8c21
Signed-off-by: Aleksandr Emelenko <emelenko.aleksandr@huawei.com>
---
 runtime/class_linker.cpp | 52 ++++++++++++++++++++++++++--------------
 1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/runtime/class_linker.cpp b/runtime/class_linker.cpp
index 0194f2e77..b02150766 100644
--- a/runtime/class_linker.cpp
+++ b/runtime/class_linker.cpp
@@ -494,10 +494,19 @@ bool ClassLinker::LoadFields(Class *klass, panda_file::ClassDataAccessor *data_a
 }
 
 template <bool reverse_layout = false>
-static void LayoutFieldsWithoutAlignment(size_t size, size_t *offset, size_t *space, PandaList<Field *> *fields)
+static void LayoutFieldsWithoutAlignment(size_t size, size_t *offset, size_t *space, PandaVector<Field *> *fields)
 {
-    while ((space == nullptr || *space >= size) && !fields->empty()) {
-        Field *field = fields->front();
+    auto last_proceeded_element = fields->end();
+    // Iterating from beginning to end and erasing elements from the beginning of a vector
+    // is required for correct field layout between language class representation in C++ code
+    // and generated by methods in class linker.
+    // (e.g. class String should have length field before hash field, not vice versa)
+    for (auto i = fields->begin(); i != fields->end(); i++) {
+        if (!(space == nullptr || *space >= size)) {
+            last_proceeded_element = i;
+            break;
+        }
+        Field *field = *i;
         // NOLINTNEXTLINE(readability-braces-around-statements)
         if constexpr (reverse_layout) {
             *offset -= size;
@@ -510,11 +519,11 @@ static void LayoutFieldsWithoutAlignment(size_t size, size_t *offset, size_t *sp
         if (space != nullptr) {
             *space -= size;
         }
-        fields->pop_front();
     }
+    fields->erase(fields->begin(), last_proceeded_element);
 }
 
-static uint32_t LayoutReferenceFields(size_t size, size_t *offset, const PandaList<Field *> &fields)
+static uint32_t LayoutReferenceFields(size_t size, size_t *offset, const PandaVector<Field *> &fields)
 {
     uint32_t volatile_fields_num = 0;
     // layout volatile fields firstly
@@ -534,10 +543,10 @@ static uint32_t LayoutReferenceFields(size_t size, size_t *offset, const PandaLi
     return volatile_fields_num;
 }
 
-static size_t LayoutFieldsInBaseClassPadding(Class *klass, PandaList<Field *> *tagged_fields,
-                                             PandaList<Field *> *fields64, PandaList<Field *> *fields32,
-                                             PandaList<Field *> *fields16, PandaList<Field *> *fields8,
-                                             PandaList<Field *> *ref_fields, bool is_static)
+static size_t LayoutFieldsInBaseClassPadding(Class *klass, PandaVector<Field *> *tagged_fields,
+                                             PandaVector<Field *> *fields64, PandaVector<Field *> *fields32,
+                                             PandaVector<Field *> *fields16, PandaVector<Field *> *fields8,
+                                             PandaVector<Field *> *ref_fields, bool is_static)
 {
     constexpr size_t SIZE_64 = sizeof(uint64_t);
     constexpr size_t SIZE_32 = sizeof(uint32_t);
@@ -573,9 +582,9 @@ static size_t LayoutFieldsInBaseClassPadding(Class *klass, PandaList<Field *> *t
     return align_offset;
 }
 
-static size_t LayoutFields(Class *klass, PandaList<Field *> *tagged_fields, PandaList<Field *> *fields64,
-                           PandaList<Field *> *fields32, PandaList<Field *> *fields16, PandaList<Field *> *fields8,
-                           PandaList<Field *> *ref_fields, bool is_static)
+static size_t LayoutFields(Class *klass, PandaVector<Field *> *tagged_fields, PandaVector<Field *> *fields64,
+                           PandaVector<Field *> *fields32, PandaVector<Field *> *fields16,
+                           PandaVector<Field *> *fields8, PandaVector<Field *> *ref_fields, bool is_static)
 {
     constexpr size_t SIZE_64 = sizeof(uint64_t);
     constexpr size_t SIZE_32 = sizeof(uint32_t);
@@ -637,12 +646,19 @@ static size_t LayoutFields(Class *klass, PandaList<Field *> *tagged_fields, Pand
 bool ClassLinker::LayoutFields(Class *klass, Span<Field> fields, bool is_static,
                                [[maybe_unused]] ClassLinkerErrorHandler *error_handler)
 {
-    PandaList<Field *> tagged_fields;
-    PandaList<Field *> fields64;
-    PandaList<Field *> fields32;
-    PandaList<Field *> fields16;
-    PandaList<Field *> fields8;
-    PandaList<Field *> ref_fields;
+    // These containers must be optimized
+    PandaVector<Field *> tagged_fields;
+    PandaVector<Field *> fields64;
+    PandaVector<Field *> fields32;
+    PandaVector<Field *> fields16;
+    PandaVector<Field *> fields8;
+    PandaVector<Field *> ref_fields;
+    tagged_fields.reserve(fields.size());
+    fields64.reserve(fields.size());
+    fields32.reserve(fields.size());
+    fields16.reserve(fields.size());
+    fields8.reserve(fields.size());
+    ref_fields.reserve(fields.size());
 
     for (auto &field : fields) {
         auto type = field.GetType();
-- 
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